We propose Chronos $^{{\mathbf +}}$ + , an accurate blockchain-based time-stamping scheme for outsourced data, where both the storage and time-stamping services are provided by cloud service providers. Specifically, Chronos $^{{\mathbf +}}$ + integrates a file into a transaction on a blockchain once the file is created, which guarantees the file's latest creation time to be the time when the block containing the transaction is appended to the blockchain. A sufficient number of consecutive blocks that are latest confirmed on the blockchain is embedded into the file at the creation time. These blocks serve as a time-dependent random seed to prove the earliest creation time, due to blockchains’ chain quality property. Chronos $^{{\mathbf +}}$ + makes the file's timestamp corresponding to a time interval formed by the earliest and latest creation times which are derived from the heights of the corresponding blocks. Due to blockchains’ chain growth property, such a height-derived timestamp can ensure that the time intervals’ range is within a few minutes so as to guarantee the accuracy. We also point out potential threats towards outsourced time-sensitive files and present security analyses to prove that Chronos $^{{\mathbf +}}$ + is secure against these threats. Comprehensive performance evaluations demonstrate the efficiency and practicality of Chronos $^{{\mathbf +}}$ + .

中文翻译：

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Chronos+：一种准确的基于区块链的云存储时间戳方案

我们提出了 Chronos $^{{\mathbf +}}$ + ，这是一种基于区块链的准确外包数据时间戳方案，其中存储和时间戳服务均由云服务提供商提供。具体来说，Chronos $^{{\mathbf +}}$ + 一旦文件被创建就将文件集成到区块链上的交易中，这保证了文件的最新创建时间是包含交易的块被附加到区块链的时间。区块链。在创建时将在区块链上最新确认的足够数量的连续块嵌入到文件中。由于区块链的链质量属性，这些块作为时间相关的随机种子来证明最早的创建时间。Chronos $^{{\mathbf +}}$ + 使文件' s 时间戳对应于由最早和最晚创建时间形成的时间间隔，该时间间隔来自相应块的高度。由于区块链的链增长特性，这种高度衍生的时间戳可以保证时间间隔的范围在几分钟内，从而保证准确性。我们还指出了对外包的时间敏感文件的潜在威胁，并提供了安全分析，以证明 Chronos $^{{\mathbf +}}$ + 可以安全地抵御这些威胁。综合性能评估证明了 Chronos $^{{\mathbf +}}$ + 的效率和实用性。这种高度衍生的时间戳可以保证时间间隔的范围在几分钟内，从而保证准确性。我们还指出了对外包的时间敏感文件的潜在威胁，并提供了安全分析，以证明 Chronos $^{{\mathbf +}}$ + 可以安全地抵御这些威胁。综合性能评估证明了 Chronos $^{{\mathbf +}}$ + 的效率和实用性。这种高度衍生的时间戳可以保证时间间隔的范围在几分钟内，从而保证准确性。我们还指出了对外包的时间敏感文件的潜在威胁，并提供了安全分析，以证明 Chronos $^{{\mathbf +}}$ + 可以安全地抵御这些威胁。综合性能评估证明了 Chronos $^{{\mathbf +}}$ + 的效率和实用性。